I have created a wizard that started as a JFrame visual class. Later on I
wish I had created it as a JPanel visual class so that I could import and
use it in different places. I tried to manually change the class from
JFrame to JPanel and 'mimic' everything to be as if a JPanel would do it
but no luck. When I open the manually modified file, the JPanel shown on
the canvas is blank while in my initialize method I have many components
added to it.

The general question in here is how one would convert a JFrame to a
JPanel? Ideally the new JPanel would contain everything that the JFrame's
content pane was containing.